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J Winkel

Publications and source records attributed to J Winkel.

40 records · Page 3Linked to original sources
PubMed1985

Comparison of office chairs with fixed forwards or backwards inclining, or tiltable seats.

Three adjustments of an office chair seat: one inclining +10 degrees (forwards), one inclining -5 degrees (backwards), and one being freely tiltable from -8 degrees to +19.5 degrees were investigated using two groups of healthy female workers in a field (n = 12), and a laboratory study (n = 10), respectively. The seat adjustments were examined with regard to effects on foot swelling, lumbar muscular load, backrest pressure and subjective acceptability. Desk-work and typing were compared according to lumbar muscular activity, seat movements (tiltable seat), and backrest pressure. Foot swelling tended to increase with increasing seat height but was not influenced by the ability to tilt the seat or not. With the different seat adjustments lumbar muscular activity did not change systematically in spite of greater backrest pressure when the seat inclined backwards. The tiltable seat was preferred to the others. Typing was associated with a more constrained and tens posture than desk work, because movements, transferred to the tiltable seat, decreased and the muscular load increased. Backrest pressure was highest during typing. A tendency towards gradually increasing restlessness (i.e. seat movements) and increasing forward inclination of the tiltable seat with time was observed.

Adult↗
PubMed1984

A method for electromyographic analysis of muscular contraction frequencies.

A method for evaluation of muscular contraction frequencies during prolonged work is presented. It is based upon computer-aided electromyographic (EMG) analyses. Variations in muscular tension, expressed as the relative force of contraction or torque in the joint, are followed using previously described EMG techniques. The number of times muscular tension crosses an amplitude band from below is then estimated. The band represents a predetermined range of amplitude. It is moved in steps from the lowest to the highest force level which occurred during the work task, and the frequency of band-crossings is computed for each band position. The frequencies are then plotted against the force levels at which the upper limit of the band was placed. From this relationship a frequency/force index is computed. The analysis is repeated several times using different band-widths. Thus, the method considers the contraction frequencies according to the load levels. It was developed to study the function of the musculo-venous pump in the legs during prolonged sedentary work, but might also be used to analyse such factors as muscular strain during work.

Adult↗
PubMed1983

On the manual handling of wide-body carts used by cabin attendants in civil aircraft.

A study was made of manual handling of wide-body carts used in civil aircraft. Under laboratory conditions, 11 females adjusted their pushing and pulling forces on fixed carts to the maximum amount they perceived as acceptable with repeated exertions. Subsequently their ability to push and pull the carts was tested with maximum exertions. The initial forces required to just get a fully loaded cart in motion were measured for different inclinations of the floor on which the cart stood. In a DC-9 aircraft, floor inclination and flying speed were measured while climbing to cruising altitude and during descent prior to landing. The maximum acceptable force for repetitive exertions was, on average, 68 N. The maximum force was, on average, 270 N. No significant differences were found between the pushing and pulling forces. The findings in the experiments caused the Swedish National Board of Occupational Safety and Health to reduce its recommended limit for repetitive push and pull in this task from 200 N to 100 N. As a result the handling of wide-body carts in the DC-9 should be delayed until at least 14-15 minutes after take-off to fulfil the new recommendation. On short flights, for which the DC-9 is used, this is not possible without reducing the level of service. A follow-up project on the development of an improved cart is under way, incorporating changes suggested in this paper and elsewhere.

Journal Article↗